This invention relates to a core and contact assembly and, more particularly, to a unitized core and contact assembly for a solenoid switch for use in a coaxial engine starter apparatus, for example, in which a solenoid switch is disposed behind an electric motor.
A conventional coaxial engine starter apparatus is constructed as illustrated in FIG. 1. Generally, the coaxial starter apparatus is arranged such that an armature rotary shaft 2 of a d.c. electric motor 1 is made hollow, a push rod 4 supported by a plunger rod 3a of a solenoid switch 3 disposed at the rear end of the d.c. motor 1 is inserted into an inner passage 2a of the armature rotary shaft 2 so that it abuts against an output rotary shaft 5, which is coaxially disposed at the front end of the armature rotary shaft 2, at an end face of the rear end portion of the output rotary shaft 5 inserted into the inner passage 2a of the armature rotary shaft 2, thereby allowing the output rotary shaft 5 to be pushed forward.
In this coaxial starter apparatus, a commutator 6 is mounted at the rear portion of the armature rotary shaft 2a, and a brush 9 supported by a holder 8 secured a mounting plate 7 is arranged to slidably contact the circumferential surface of the commutator 6. Behind a commutator assembly including the commutator 6, the brush 9 and the holder 8 and between the solenoid switch 3, a terminal assembly 11 in which two terminal bolts 10 (only one of the terminal bolts is illustrated in FIG. 1) are molded within a resin material is mounted at a notch formed in the circumferential surface of a rear bracket 1b, and on one side face of this terminal assembly 11, two stationary contacts 13 and 14 which can be short-circuited by a movable contact 12 of the solenoid switch 3 are disposed to project therefrom. These stationary contacts 13 and 14 are respectively formed integral with the terminal bolts 10 and therefore electrically conductive to each terminal bolt 10.
As for these two terminal bolts 10, one of them is connected by a wire to a battery mounted on the vehicle, and the other of them is connected by a wire to the positive side brush 9 as well as to a lead-in portion of an excitation coil 15 of the solenoid switch 3.
In FIG. 1, reference numeral 16 is a pinion mounted at the front end portion of the output rotary shaft 5 capable of engaging and disengaging an engine ring gear (not shown) by a reciprocating motion of the output rotary shaft 5, 17 is a planetary speed reduction gear for reducing the rotational speed of the armature rotary shaft 2, 18 is an over-running clutch assembly for transmitting the rotation speed-reduced at the planetary speed reduction gear 17 to the output rotary shaft 5 and for preventing reverse transmission of the high speed rotation of the engine from the output rotary shaft 5 to the d.c. electric motor 1.
However, in the coaxial starter apparatus as previously described, since the terminal assembly 11 and the core 19 which is one of the components of the solenoid switch 3 are constructed as separate components, the cost due to the increased number of parts is increased and, in addition, since a magnetic attractive force generating portion 19a (the hatched area in FIG. 2) is formed evading the contacts 13 and 14 to expose them (in other words, though partially, the stationary contacts are present inside thereof, so that the attractive force generating portion 19a cannot enter into the interior region), the thickness in the radial direction of the magnetic attractive force generating portion 19a is very thin due to the dimensional problem in conjunction with the inner diameter of the bushing 3b slidably supporting the plunger 20 of the solenoid switch 3, whereby the resulting magnetic cross sectional area is disadvantageously small and it is not possible to obtain a large magnetic attractive force.